Senior Backend Engineer

About Tesouro

Tesouro builds the embedded banking and FinOps infrastructure that lets banks and software platforms launch financial products without rebuilding the plumbing underneath. We sit in the critical path of real money movement which includes payments, ledgers, invoicing, and the APIs our partners build their businesses on. Our work involves high trust and high stakes.

We’re a small, senior team that ships daily. Product defines the target, and you own the execution. We are expanding our team with engineers who can step in and take absolute ownership of the technical solutions.

The role

You’ll work across our microservices architecture, make architecture decisions alongside the rest of the team, and have a direct hand in what we build for partners. We don't hand down hyper-prescriptive tickets, but we don't expect you to guess, either. We need engineers who take a problem, actively design and iterate with Product, and ship robust solutions.

What you’ll do

• Design, build, and operate backend services across our microservices platform
• Own features end to end: from shaping the approach with product and other engineers, through implementation, testing, deployment, monitoring, metrics, runbooks, and support. 
• Make architecture choices collaboratively: we move fast, but we talk through the decisions that are hard to reverse.
• Integrate with partner banks, card networks, and third-party providers, and help our partners succeed on top of what you build.
• Incorporate AI tools into your day-to-day workflow: planning, coding, testing, and technical documentation and help the team think critically about where AI assistance improves quality versus where it introduces risk.
• Embed reliability into our daily workflow by continuously expanding test coverage and analyzing CI/CD pipelines to safeguard every rollout.

What we’re looking for

• Senior level or higher. You’ve owned significant backend systems in production and have the judgment that comes with it.
• Highly autonomous, and a strong collaborator. You can run with ambiguity without going dark. You know when to pull someone in before a hard-to-reverse call, rather than disappearing into a prompt.
• A genuine builder and fast learner. You ramp quickly on unfamiliar domains and you’d rather understand the why than just close the ticket.
• AI-fluent, human-led. You get real leverage from AI tooling without handing over your judgment . You lead the model; you don’t follow it.
• Comfortable in a distributed systems / microservices world. APIs, asynchronous messaging, relational and non-relational data, and the failure modes that come with all of it.
• US-based. Cincinnati or Boston is preferred, as is anywhere we already operate, but we’ll talk to strong candidates anywhere in the continental US.

Bonus points

Bonus points if you know of the areas below as well!

• AWS/EKS Experience
• Experience with React/JS Frameworks
• Experience inpayments, banking, or fintech

Our stack

Our backend is primarilyC# /.NET withPython in the mix, running as microservices onAWS andKubernetes (EKS). We usePostgreSQL as our relational core andCassandra for high-throughput transaction processing, withRedis,RabbitMQ, andKafka moving data between services. Our frontend web applications run onReact in anNX monorepo.

We ship throughArgoCD andGitHub Actions, lean hard on automated testing (PACT contract tests,xUnit,Cucumber/Jest,Playwright), and run observability onGrafana andOpenTelemetry withPagerDuty for alerting. We’rePCI DSS v4.0 andSOC 2 certified, and security is a design requirement here, not an afterthought.

How we think about AI

We use AI tooling in every phase of engineering, but we use it skeptically.  Very few PRs are opened without some correction & improvement from our engineers.  We expect engineers to orchestrate with it for brainstorming, prototyping, boilerplate, and test generation: anything that lets you spend more of your time on the hard problems.  At the same time, your peers are your most valuable collaborators. What we don’t do is treat AI output as a finished product or a substitute for judgment. In fintech, correctness matters and money movements must be correct, a generated solution that’s 95% right isn’t good enough. We want engineers who know the difference, push back where AI missed the mark, and still find ways to ship faster because of the tools at their disposal.  AI did it is never an excuse.